In recent years, in the medical field, various treatments and tests are performed by using a medical instrument that is called a catheter and has a shape of an elongated, soft hollow tube. Examples of treatment methods include a method in which a medication is directly administered to an affected area by utilizing the elongated shape of a catheter, a method in which a stenosed part in a body cavity is pushed to be dilated by using a catheter having a distal end to which a balloon dilated by pressurizing is attached, a method in which an affected area is scraped off by using a catheter having a distal part to which a cutter is attached, and a method in which, conversely, an aneurysm, bleeding site, or feeding vessel is stuffed to be closed by using a catheter. Furthermore, there is e.g. a treatment method in which a stent having a shape of a tube whose side surface has a mesh shape is buried and indwelled in a body cavity by using a catheter in order to keep a stenosed part in a biological lumen at an opened state. Moreover, an excess liquid for the inside of a body is often sucked via a catheter.
To perform the above-described procedures, the catheter distal part needs to be made to reach the target site. However, biological lumens such as tracheae, digestive tracts, and blood vessels are intricate with bifurcations and therefore it is difficult to make the catheter distal part reach the target site. Therefore, it is important to control the curving direction of the catheter distal part.
As a technique relating to this, a catheter having a housing provided with a piston chamber at the distal part is described in Patent Document 1 to be shown below. According to this technique, a piston provided in the piton chamber moves in the length direction relative to the housing to thereby curve the catheter distal part. Furthermore, in Patent Document 2 to be shown below, a catheter having a control handle to which a first pull wire anchor and a second pull wire anchor are joined and a thumb control unit to control the movement of this control handle in the length direction is described. According to this technique, the catheter distal part is curved by pressing the thumb control unit to move the control handle in the length direction.